import SwiftUI
import UniformTypeIdentifiers

struct ChatView: View {
    @Bindable var viewModel: ChatViewModel
    @FocusState private var isInputFocused: Bool
    @State private var isShowingFilePicker = false
    @State private var isDragOver = false
    @State private var previewImageURL: URL?

    var body: some View {
        HStack(spacing: 0) {
            // Recent images sidebar
            if !viewModel.recentImages.isEmpty {
                recentImagesSidebar
                Divider()
            }

            // Main chat area
            VStack(spacing: 0) {
                // Messages list
                ScrollViewReader { proxy in
                    ScrollView {
                        LazyVStack(spacing: 12) {
                            ForEach(viewModel.messages) { message in
                                MessageBubble(message: message)
                                    .id(message.id)
                            }
                        }
                        .padding()
                    }
                    .onChange(of: viewModel.messages.count) { _, _ in
                        if let lastMessage = viewModel.messages.last {
                            withAnimation {
                                proxy.scrollTo(lastMessage.id, anchor: .bottom)
                            }
                        }
                    }
                    .onChange(of: viewModel.messages.last?.content) { _, _ in
                        if let lastMessage = viewModel.messages.last {
                            withAnimation {
                                proxy.scrollTo(lastMessage.id, anchor: .bottom)
                            }
                        }
                    }
                }

                // Error message
                if let error = viewModel.errorMessage {
                    HStack {
                        Image(systemName: "exclamationmark.triangle.fill")
                            .foregroundStyle(.yellow)
                        Text(error)
                            .font(.caption)
                            .foregroundStyle(.secondary)
                        Spacer()
                        Button("Dismiss") {
                            viewModel.errorMessage = nil
                        }
                        .buttonStyle(.plain)
                        .font(.caption)
                    }
                    .padding(.horizontal)
                    .padding(.vertical, 8)
                    .background(.red.opacity(0.1))
                }

                Divider()

                // Pending images preview
                if !viewModel.pendingImages.isEmpty {
                    pendingImagesView
                }

                // Input area
                inputArea
            }
            .onDrop(of: [.fileURL, .image], isTargeted: $isDragOver) { providers in
                handleDrop(providers: providers)
                return true
            }
            .overlay {
                if isDragOver {
                    RoundedRectangle(cornerRadius: 8)
                        .stroke(Color.accentColor, lineWidth: 3)
                        .background(Color.accentColor.opacity(0.1))
                        .padding(4)
                }
            }
        }
        .frame(minWidth: 500, minHeight: 500)
        .toolbar {
            ToolbarItem(placement: .primaryAction) {
                Button {
                    viewModel.loadRecentImages()
                } label: {
                    Image(systemName: "arrow.clockwise")
                }
                .help("Refresh recent images")
            }
            ToolbarItem(placement: .primaryAction) {
                Button {
                    viewModel.clearChat()
                } label: {
                    Image(systemName: "trash")
                }
                .help("Clear chat")
                .disabled(viewModel.messages.isEmpty)
            }
        }
        .task {
            await viewModel.initialize()
        }
        .onAppear {
            NSApp.setActivationPolicy(.regular)
            NSApp.activate(ignoringOtherApps: true)

            DispatchQueue.main.asyncAfter(deadline: .now() + 0.2) {
                if let window = NSApp.windows.first(where: { $0.title == "Chat" }) {
                    window.makeKeyAndOrderFront(nil)
                }
                isInputFocused = true
            }
        }
        .onDisappear {
            if NSApp.windows.filter({ $0.isVisible && $0.title != "" }).isEmpty {
                NSApp.setActivationPolicy(.accessory)
            }
        }
        .fileImporter(
            isPresented: $isShowingFilePicker,
            allowedContentTypes: ChatViewModel.supportedImageTypes,
            allowsMultipleSelection: true
        ) { result in
            switch result {
            case .success(let urls):
                for url in urls {
                    if url.startAccessingSecurityScopedResource() {
                        viewModel.addImage(from: url)
                        url.stopAccessingSecurityScopedResource()
                    }
                }
            case .failure(let error):
                viewModel.errorMessage = error.localizedDescription
            }
        }
        .sheet(item: $previewImageURL) { url in
            ImagePreviewSheet(url: url) {
                viewModel.addRecentImage(url)
                previewImageURL = nil
            } onCancel: {
                previewImageURL = nil
            }
        }
    }

    // MARK: - Drag & Drop Handler

    private func handleDrop(providers: [NSItemProvider]) {
        for provider in providers {
            // Try to load as file URL first
            if provider.hasItemConformingToTypeIdentifier(UTType.fileURL.identifier) {
                provider.loadItem(forTypeIdentifier: UTType.fileURL.identifier, options: nil) { item, error in
                    guard error == nil else { return }

                    if let data = item as? Data,
                       let url = URL(dataRepresentation: data, relativeTo: nil) {
                        DispatchQueue.main.async {
                            viewModel.addImage(from: url)
                        }
                    } else if let url = item as? URL {
                        DispatchQueue.main.async {
                            viewModel.addImage(from: url)
                        }
                    }
                }
            }
            // Try to load as image data
            else if provider.hasItemConformingToTypeIdentifier(UTType.image.identifier) {
                provider.loadDataRepresentation(forTypeIdentifier: UTType.image.identifier) { data, error in
                    guard let data = data, error == nil else { return }
                    DispatchQueue.main.async {
                        let attachment = ImageAttachment(data: data, filename: "dropped_image.png")
                        if viewModel.pendingImages.count < 5 {
                            viewModel.pendingImages.append(attachment)
                        }
                    }
                }
            }
        }
    }

    // MARK: - Recent Images Sidebar

    private var recentImagesSidebar: some View {
        VStack(alignment: .leading, spacing: 8) {
            Text("Recent")
                .font(.headline)
                .foregroundStyle(.secondary)
                .padding(.horizontal, 8)
                .padding(.top, 8)

            ScrollView {
                LazyVStack(spacing: 8) {
                    ForEach(viewModel.recentImages, id: \.self) { url in
                        RecentImageThumbnail(url: url) {
                            previewImageURL = url
                        }
                    }
                }
                .padding(.horizontal, 8)
                .padding(.bottom, 8)
            }
        }
        .frame(width: 100)
        .background(Color(nsColor: .controlBackgroundColor).opacity(0.5))
    }

    // MARK: - Pending Images Preview

    private var pendingImagesView: some View {
        ScrollView(.horizontal, showsIndicators: false) {
            HStack(spacing: 8) {
                ForEach(viewModel.pendingImages) { attachment in
                    pendingImageThumbnail(attachment)
                }
            }
            .padding(.horizontal)
            .padding(.vertical, 8)
        }
        .background(Color(nsColor: .controlBackgroundColor))
    }

    private func pendingImageThumbnail(_ attachment: ImageAttachment) -> some View {
        ZStack(alignment: .topTrailing) {
            if let thumbnail = attachment.thumbnail {
                Image(nsImage: thumbnail)
                    .resizable()
                    .aspectRatio(contentMode: .fill)
                    .frame(width: 60, height: 60)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
            } else {
                RoundedRectangle(cornerRadius: 8)
                    .fill(Color.gray.opacity(0.3))
                    .frame(width: 60, height: 60)
                    .overlay {
                        Image(systemName: "photo")
                            .foregroundStyle(.secondary)
                    }
            }

            Button {
                viewModel.removePendingImage(attachment)
            } label: {
                Image(systemName: "xmark.circle.fill")
                    .font(.system(size: 16))
                    .foregroundStyle(.white)
                    .background(Circle().fill(.black.opacity(0.6)).frame(width: 18, height: 18))
            }
            .buttonStyle(.plain)
            .offset(x: 6, y: -6)
        }
    }

    // MARK: - Input Area

    private var inputArea: some View {
        HStack(spacing: 8) {
            Button {
                isShowingFilePicker = true
            } label: {
                Image(systemName: "photo.badge.plus")
                    .font(.title3)
                    .foregroundStyle(.secondary)
            }
            .buttonStyle(.plain)
            .help("Add image")

            Button {
                viewModel.addImageFromPasteboard()
            } label: {
                Image(systemName: "doc.on.clipboard")
                    .font(.title3)
                    .foregroundStyle(.secondary)
            }
            .buttonStyle(.plain)
            .help("Paste image from clipboard")

            TextField("Message...", text: $viewModel.inputText, axis: .vertical)
                .textFieldStyle(.plain)
                .lineLimit(1...5)
                .focused($isInputFocused)
                .onSubmit {
                    if viewModel.canSend {
                        viewModel.sendMessage()
                    }
                }

            if viewModel.isLoading {
                Button {
                    viewModel.stopGeneration()
                } label: {
                    Image(systemName: "stop.circle.fill")
                        .font(.title2)
                        .foregroundStyle(.red)
                }
                .buttonStyle(.plain)
            } else {
                Button {
                    viewModel.sendMessage()
                } label: {
                    Image(systemName: "arrow.up.circle.fill")
                        .font(.title2)
                        .foregroundStyle(viewModel.canSend ? Color.accentColor : Color.gray)
                }
                .buttonStyle(.plain)
                .disabled(!viewModel.canSend)
            }
        }
        .padding()
    }
}

// MARK: - Recent Image Thumbnail

struct RecentImageThumbnail: View {
    let url: URL
    let onTap: () -> Void

    @State private var thumbnail: NSImage?

    var body: some View {
        Button(action: onTap) {
            ZStack {
                if let thumbnail = thumbnail {
                    Image(nsImage: thumbnail)
                        .resizable()
                        .aspectRatio(contentMode: .fill)
                        .frame(width: 80, height: 80)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                } else {
                    RoundedRectangle(cornerRadius: 8)
                        .fill(Color.gray.opacity(0.3))
                        .frame(width: 80, height: 80)
                        .overlay {
                            ProgressView()
                                .scaleEffect(0.6)
                        }
                }
            }
        }
        .buttonStyle(.plain)
        .help(url.lastPathComponent)
        .task {
            await loadThumbnail()
        }
    }

    private func loadThumbnail() async {
        guard let image = NSImage(contentsOf: url) else { return }

        let maxSize: CGFloat = 80
        let ratio = min(maxSize / image.size.width, maxSize / image.size.height, 1.0)
        let newSize = NSSize(
            width: image.size.width * ratio,
            height: image.size.height * ratio
        )

        let thumb = NSImage(size: newSize)
        thumb.lockFocus()
        image.draw(
            in: NSRect(origin: .zero, size: newSize),
            from: NSRect(origin: .zero, size: image.size),
            operation: .copy,
            fraction: 1.0
        )
        thumb.unlockFocus()

        await MainActor.run {
            thumbnail = thumb
        }
    }
}

// MARK: - Message Bubble

struct MessageBubble: View {
    let message: ChatMessage
    @State private var showCopied = false

    var body: some View {
        HStack {
            if message.role == .user {
                Spacer(minLength: 60)
            }

            VStack(alignment: message.role == .user ? .trailing : .leading, spacing: 4) {
                if !message.images.isEmpty {
                    imageGrid
                }

                if !message.content.isEmpty {
                    Text(message.content)
                        .textSelection(.enabled)
                        .padding(.horizontal, 12)
                        .padding(.vertical, 8)
                        .background(bubbleColor)
                        .foregroundStyle(message.role == .user ? .white : .primary)
                        .clipShape(RoundedRectangle(cornerRadius: 16))
                }

                if message.isStreaming {
                    HStack(spacing: 4) {
                        ProgressView()
                            .scaleEffect(0.6)
                        Text("Generating...")
                            .font(.caption2)
                            .foregroundStyle(.secondary)
                    }
                }

                // Copy button for assistant messages
                if message.role == .assistant && !message.content.isEmpty && !message.isStreaming {
                    HStack {
                        Spacer()
                        Button {
                            NSPasteboard.general.clearContents()
                            NSPasteboard.general.setString(message.content, forType: .string)
                            showCopied = true
                            DispatchQueue.main.asyncAfter(deadline: .now() + 1.5) {
                                showCopied = false
                            }
                        } label: {
                            HStack(spacing: 4) {
                                Image(systemName: showCopied ? "checkmark" : "doc.on.doc")
                                Text(showCopied ? "Copied" : "Copy")
                            }
                            .font(.caption)
                            .foregroundStyle(.secondary)
                        }
                        .buttonStyle(.plain)
                    }
                    .padding(.top, 2)
                }
            }

            if message.role == .assistant {
                Spacer(minLength: 60)
            }
        }
    }

    @ViewBuilder
    private var imageGrid: some View {
        let columns = min(message.images.count, 3)
        LazyVGrid(
            columns: Array(repeating: GridItem(.flexible(), spacing: 4), count: columns),
            spacing: 4
        ) {
            ForEach(message.images) { attachment in
                if let thumbnail = attachment.thumbnail {
                    Image(nsImage: thumbnail)
                        .resizable()
                        .aspectRatio(contentMode: .fill)
                        .frame(width: 80, height: 80)
                        .clipShape(RoundedRectangle(cornerRadius: 8))
                }
            }
        }
        .padding(4)
        .background(
            message.role == .user
                ? Color.accentColor.opacity(0.8)
                : Color(nsColor: .controlBackgroundColor)
        )
        .clipShape(RoundedRectangle(cornerRadius: 12))
    }

    private var bubbleColor: Color {
        switch message.role {
        case .user:
            return .accentColor
        case .assistant:
            return Color(nsColor: .controlBackgroundColor)
        }
    }
}

// MARK: - Image Preview Sheet

struct ImagePreviewSheet: View {
    let url: URL
    let onConfirm: () -> Void
    let onCancel: () -> Void

    @State private var image: NSImage?

    var body: some View {
        VStack(spacing: 16) {
            Text("Add Image")
                .font(.headline)

            if let image = image {
                Image(nsImage: image)
                    .resizable()
                    .aspectRatio(contentMode: .fit)
                    .frame(maxWidth: 500, maxHeight: 400)
                    .clipShape(RoundedRectangle(cornerRadius: 8))
                    .shadow(radius: 4)
            } else {
                RoundedRectangle(cornerRadius: 8)
                    .fill(Color.gray.opacity(0.2))
                    .frame(width: 300, height: 200)
                    .overlay {
                        ProgressView()
                    }
            }

            Text(url.lastPathComponent)
                .font(.caption)
                .foregroundStyle(.secondary)
                .lineLimit(1)

            HStack(spacing: 16) {
                Button("Cancel") {
                    onCancel()
                }
                .keyboardShortcut(.cancelAction)

                Button("Add to Message") {
                    onConfirm()
                }
                .keyboardShortcut(.defaultAction)
                .buttonStyle(.borderedProminent)
            }
        }
        .padding(24)
        .frame(minWidth: 400, minHeight: 300)
        .task {
            image = NSImage(contentsOf: url)
        }
    }
}

// MARK: - URL Identifiable Extension

extension URL: @retroactive Identifiable {
    public var id: String { absoluteString }
}